In an electrophotographic image forming apparatus such as a digital copier and a printer, since image quality is remarkably affected, a photoreceptor drum is replaced periodically or as needed. However, mainly because the photoreceptor drum includes a hazardous substance, measures of taking care not to directly touch the photoreceptor drum at the time of the replacement, or preventing waste toner from a cleaning device from causing a surrounding area to be contaminated at the time of removal of the photoreceptor drum are required, so that the handling of the photoreceptor drum is difficult and the replacement of the photoreceptor drum has been performed at the time of maintenance by a serviceman.
Therefore, since the replacement operation of a photoreceptor drum always has to be performed by a serviceman on request, which causes inconvenience, in recent years, a device in which image forming portions such as a photoreceptor drum, and a cleaning device, a charger, and a developing device that are arranged around the photoreceptor drum are formed as a cartridge type process unit and integrally handled, which simplifies maintenance and enables the replacement of a photoreceptor drum to be easily performed not only by a serviceman but also by a user has been developed (see Patent Literature 1, for example). In such a process unit, when the photoreceptor drum reaches the end of a life span and a user performs the replacement of the photoreceptor drum, the entire process unit has been replaced and a used process unit has been discarded as it is.